Abstract
MOM1 is required for transcriptional gene silencing of a subset of endogenous repetitive elements and transgenes in Arabidopsis thaliana. Although the repetitiveness of the targets of MOM1 had made the analysis complicated, a recent identification of an endogenous single-copy target of MOM1 allowed us to dissect the mechanism of the silencing mediated by MOM1 in detail. We found that, in the mom1 mutants, Cyclophilin 40 (CyP40) gene accumulated longer RNA molecules that were not seen in the wild type plants. Accumulation of these RNAs was not accompanied by changes in methyaltion of histone H3 at K4, K9 and K27 in the template. Detailed analysis of the accumulated RNAs showed that the CyP40 RNA were trans-spliced even in the wild type plants.
